Lysosomes are vacuolar organelles responsible for the breakdown of lipids, proteins, sugars, and other cellular material into their constituent components. To degrade intracellular organelles, lysosomes fuse with autophagosomes to form autolysosomes, while extracellular cargo marked for further processing and degradation is directed to the lysosome from the endolysosomal pathway itself. In addition, lysosomes are involved in nutrient sensing of engulfed amino acids. During starvation, mTORC1 is inhibited and autophagy is induced, thus indicating lysosomes as a link between nutrient availability and signaling pathways related to cell growth.
A growing body of work implicates lysosomal dysfunction in a range of pathologies. Dysfunction in the ability of lysosomes to catabolize or export their contents results in lysosomal storage disorders, a family of diseases characterized by pathologies caused by the accumulation of undigested substrates. Lysosomal cholesterol accumulation is causal during inflammation in both atherosclerosis and non-alcoholic steatohepatitis. Defects in the fusion of lysosomes with autophagosomes leads to an accumulation of autolysosomes in the neurons of patients with amyotrophic lateral sclerosis (ALS), while impaired autolysosomal proteolysis is implicated in both Alzheimer's and Parkinson's diseases. The ability to observe changes in the lipid content of lysosomes is crucial to understanding the distinct roles played by the lysosomes in such a variety of diseases. However, no one has developed and/or applied imaging or any other method to observe endogenous cholesterol and/or other lipids in live cells and animals. It would be advantageous to do so for a number of reasons including, for example, to measure and detect cholesterol and other lipids in early stage disease detection.
Spectral imaging is a powerful tool for detection, validation, separation, and quantification in applications ranging from mineral assessment of geological satellite images to semiconductor material characterization. In contrast to multi-spectral imaging in discrete wavelength bands, hyper-spectral imaging produces a full, quasi-continuous emission spectrum at every spatial pixel. Several methods exist for hyperspectral data acquisition, including pixel-by-pixel, line-by-line acquisition of spectra, or globally by acquiring separate images at each wavelength. Recent applications of global hyperspectral imaging have used volume Bragg gratings (VBG) to acquire spectrally-defined images from the scanned wavelength space, for the mapping of solar cell saturation currents and in astronomical imaging.